This invention relates to storage batteries particularly of the alkaline type and more specifically to the interelement and terminal connections therein. Shetterly U.S. Pat. No. 3,164,711 is typical of the type of batteries involved here. Shetterly discloses a nickel-cadmium battery having tabs from the several elements bundled together and projection welded to a depending portion of a battery terminal. The Shetterly technique requires unnecessary machining or the like to form the flat depending portion and welding projection and requires precise fixturing during welding to align the welding electrodes with the welding projections.
It is an object of the present invention to provide a simpler welded battery tab and terminal structure and process for making same. This and other objects and advantages of the present invention will become more readily apparent from the detailed description which follows.
In an effort to simplify the Shetterly terminal structure and assembly operation, it was initially proposed to spot weld the connecting tabs to a cylinder extension of the terminal instead of to the projection-bearing flat extension of Shetterly. Welding current concentration would thereby be effected by the line contact between the flat tab and the curved surface of the cylinder rather than by means of a discrete projection, ala Shetterly. It was found, however, that simultaneous spot welding of the tabs together and to the cylinder in this manner left the last or outermost tab in the bundle (i.e., at the distal extremity of the bundle furthest from the cylinder) poorly bonded to the penultimate tab such that the last tab was readily detachable from the bundle thereby rendering ineffective the end element in each cell. Attempts to first weld the tabs together and then as a unit to the cylinder resulted in the same problem. Moreover, attempts to better weld the outermost tab by increasing the welding power only caused metal expulsion from the weld and/or sticking of the tab to the welding electrodes.